Nowadays, with the development of economy and great improvement of people's living standard, automobiles substantially have gone into thousands of households. The automobile has became a major mode of transportation, and no matter a family automobile or a large freight car and a loading vehicle have occupied half of the transportation industry depending on irreplaceable advantages thereof. With continuous expansion of urbanization, the quantity of family cars is steadily on the increase, which leads to large-area coverage of roads. No matter an ordinary driveway or an overhead driveway has various curves. Usually, a vehicle has a rollover risk at different velocities when rounding a corner because of different cornering radiuses. However, if the vehicle can keep the cornering radius of the automobile in a safety range all the time during cornering, then the automobile may be very safe during cornering. Cornering and turning around are unavoidable during driving, and are difficult to be mastered for those with poor driving skills, and a danger is inevitable due to wrong determination. The cornering radius of the existing vehicle while steering under a low velocity condition such as turning in situ is oversize, which requires a very large space, and is very inconvenient for urban life with heavy traffic. While under a high velocity condition, friction unavoidably occurs to a rear wheel of an ordinary automobile with the guiding of a front wheel while cornering; in this way, the automobile may be unstable during cornering, and operation reliability cannot be guaranteed in case of emergency.
Chinese patent CN201420437339.3 disclosed a rear wheel active steering device and control system thereof on Dec. 3, 2014, comprising a moment amplification device assembly, a rear wheel steering system assembly, a steering knuckle and a wheel system assembly, wherein the steering knuckle is fixed on a motor shaft of a hub motor of the wheel system assembly, a steering pull rod of the steering system assembly is connected to a steering trapezoidal arm of the steering knuckle, and a support at a lower end of the moment amplification device assembly is connected to a steering transmission shaft of the rear wheel steering system assembly. The utility model is applied to an electric automobile independently driving by the hub motor, and the steering moment of the rear wheel may be amplified through the moment amplification device, so as to adapt to an occasion with steering difficulty. Meanwhile, an electric-control unit can assist in steering the rear wheel by adjusting differential of the hub motor of the rear wheel. However, such technology lacks a reasonable control strategy, which leads to relatively poor control safety; moreover, the cornering radius while steering under a low velocity condition such as turning in situ is oversize, which requires a very large space and is very inconvenient for urban life with heavy traffic. While under a high velocity condition, friction unavoidably occurs to a rear wheel of an ordinary automobile with the guiding of a front wheel while cornering; in this way, the automobile may be unstable during cornering, and operation reliability cannot be guaranteed in case of emergency.